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Astronomy Final

Terms in this set (50)

According to present understanding, which of the following statements about the solar wind is not true?


It is even stronger today than it was when the Sun was young.

It helped in the transfer of angular momentum from the young Sun to particles that blew into interstellar space, which explains why the Sun rotates so slowly today.

It consists of charged particles blown off the surface of the Sun.

It swept vast amounts of gas from the solar nebula into interstellar space.
It is even stronger today than it was when the Sun was young.
According to our theory of solar system formation, which law best explains why the central regions of the solar nebula got hotter as the nebula shrank in size?


The law of conservation of angular momentum

Newton's third law

The two laws of thermal radiation

The law of conservation of energy
The law of conservation of energy
How do scientists determine the age of the solar system?


Radiometric dating of Moon rocks.

Theoretical calculations tell us how long it has taken the planets to evolve to their present forms

Radiometric dating of the oldest Earth rocks.

Radiometric dating of meteorites
Radiometric dating of meteorites
What is the primary reason that astronomers suspect that some jovian moons were captured into their current orbits?


Astronomers have observed moons being captured.

Some moons have orbits that are "backwards" (compared to their planet's rotation) or highly inclined to their planet's equator.

Some moons are surprisingly large in size.

Some moons have a composition that differs from the composition of the planets
Some moons have orbits that are "backwards" (compared to their planet's rotation) or highly inclined to their planet's equator.
According to our present theory of solar system formation, which of the following objects now reside quite far from the place where they formed originally?


Kuiper belt comets

Oort cloud comets

Asteroids of the asteroid belt

The terrestrial planets
Oort cloud comets
According to our present theory of solar system formation, which of the following best explains why the solar nebula ended up with a disk shape as it collapsed?


It flattened as a natural consequence of collisions between particles in the nebula.

It was fairly flat to begin with, and retained this flat shape as it collapsed.

The law of conservation of energy.

The force of gravity pulled the material downward into a flat disk.
It flattened as a natural consequence of collisions between particles in the nebula.
Many meteorites appear to have formed very early in the solar system's history. How do these meteorites support our theory about how the terrestrial planets formed?


The meteorites sizes are just what we'd expect if metal and rock condensed and accreted as our theory suggests.

Their appearance and composition matches what we observe in comets today, suggesting that they were once pieces of icy planetesimals.

The meteorites appearance and composition is just what we'd expect if metal and rock condensed and accreted as our theory suggests.

Their overall composition is just what we believe the composition of the solar nebula to have been: mostly hydrogen and helium.
The meteorites appearance and composition is just what we'd expect if metal and rock condensed and accreted as our theory suggests.
Which of the following best describes the geological histories of the Moon and Mercury?


Impact cratering shaped these worlds early in their histories. Then, during the past few million years, they were reshaped by episodes of volcanism and tectonics.

Early in their histories, they suffered many impacts and experienced some volcanism and tectonics, but they now have little geological activity at all.

Impact cratering is the only major geological process that has affected their surfaces.

All four geological processes were important in their early histories, but only impact cratering still reshapes their surfaces today.
Early in their histories, they suffered many impacts and experienced some volcanism and tectonics, but they now have little geological activity at all.
Recent evidence suggests that Mars once had a global magnetic field. Assuming this is true, which of the following could explain why Mars today lacks a global magnetic field like that of Earth?


Mars is too far from the Sun to have a global magnetic field.

Mars rotates much slower than the Earth.

Mars's interior has cooled so much its molten core layer no longer undergoes convection.

The Martian core is made of rock, while Earth's core is made of metal.
Mars's interior has cooled so much its molten core layer no longer undergoes convection.
Which two factors are most important to the existence of plate tectonics on Earth?


the existence of life and oxygen in the atmosphere

mantle convection and a thin lithosphere

Earth's liquid outer core and solid inner core

oxygen in the atmosphere and mantle convection
mantle convection and a thin lithosphere
You discover an impact crater that is 10 kilometers across. Which of the following can you conclude?

It was created within the past 1 billion years.

It was created by the impact of an object about 10 kilometers across.

It was created by the impact of an object about 1 kilometer across.

It was created within the past 10 million years.
It was created by the impact of an object about 1 kilometer across.
Why is Earth's continental crust lower in density than seafloor crust?


Continental crust is made as the lowest-density seafloor crust melts and erupts to the surface near subduction zones.

Continental crust comes from Earth's inner core while seafloor crust comes from the outer core.

Continental crust comes from volcanoes while seafloor crust comes from geysers.

Continental crust is made from a low-density volcanic rock called basalt.
Continental crust is made as the lowest-density seafloor crust melts and erupts to the surface near subduction zones.
Which of the following is the underlying reason why Venus has so little wind erosion?

its relatively close distance to the Sun

its small size

its slow rotation

its thick atmosphere
its slow rotation
All the following statements about Venus are true. Which one offers evidence of a global repaving about a billion years ago?


Venus's largest features are three elevated regions that look somewhat like continents.

Venus has relatively few impact craters and these craters are distributed fairly evenly over the entire planet.

Venus appears to lack any water that could lubricate the flow of rock in its crust and mantle.

Venus has many circular features, called coronae, which appear to be tectonic in origin.
Venus has relatively few impact craters and these craters are distributed fairly evenly over the entire planet.
The choices below describe four hypothetical planets. Which one would you expect to have the most features of erosion? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.)


Size: twice as big as Earth. Distance from Sun: same as Mercury. Rotation rate: once every 6 months.

Size: same as Mars. Distance from Sun: same as Earth. Rotation rate: once every 18 hours.

Size: same as Venus. Distance from Sun: same as Mars. Rotation rate: once every 25 hours.

Size: same as the Moon. Distance from Sun: same as Mars. Rotation rate: once every 10 days.
Size: same as Venus. Distance from Sun: same as Mars. Rotation rate: once every 25 hours.
In very general terms, how do the temperature structures of the atmospheres of Venus and Mars differ from that of Earth?


They lack ultraviolet-absorbing stratospheres.

Temperatures in their tropospheres increase with altitude, rather than decreasing with altitude.

Their atmospheres are similar in structure to Earth's, but with much higher temperatures.

They lack X-ray absorbing thermospheres.
They lack ultraviolet-absorbing stratospheres.
Suppose that Earth's ice caps melted, but everything else about the Earth's surface and atmosphere stayed the same. What would happen to Earth's average surface temperature?


The surface temperature would decrease.

The surface temperature would increase.

The temperature would not be affected at all.

The surface temperature would change radically, until it was equal to the melting temperature of ice.
The surface temperature would increase.
Suppose Earth were to cool down a little. How would the carbon dioxide cycle tend to restore temperatures to normal?


Cooler temperatures mean more ice and more erosion, which somehow makes the planet warm up.

Cooler temperatures allow carbon dioxide to form rain and rain out of the atmosphere.

Cooler temperatures cause volcanoes to become more active, so they release more carbon dioxide into the atmosphere than they do when temperatures are warmer.

Cooler temperatures lead to slower formation of carbonate minerals in the ocean, so carbon dioxide released by volcanism builds up in the atmosphere and strengthens the greenhouse effect.
Cooler temperatures lead to slower formation of carbonate minerals in the ocean, so carbon dioxide released by volcanism builds up in the atmosphere and strengthens the greenhouse effect.
Which of the following best describes how the greenhouse effect works?


Greenhouse gases absorb infrared light coming from the Sun, and this absorbed sunlight heats the lower atmosphere and the surface.

Greenhouse gases absorb X-rays and ultraviolet light from the Sun, and this absorbed radiation then heats the atmosphere and the surface.

A planet's surface absorbs visible sunlight and returns this absorbed energy to space as infrared light. Greenhouse gases slow the escape of this infrared radiation, which thereby heats the lower atmosphere.

The greenhouse effect is caused primarily by ozone, which absorbs ultraviolet light and thereby makes the atmosphere much hotter than it would be otherwise.
A planet's surface absorbs visible sunlight and returns this absorbed energy to space as infrared light. Greenhouse gases slow the escape of this infrared radiation, which thereby heats the lower atmosphere.
Which of the following best explain what we think happened to outgassed water vapor on Venus?


It turned into carbon dioxide by reacting with nitrogen in Venus's atmosphere.

It is frozen as water ice in craters near the poles.

Ultraviolet light split the water molecules, and the hydrogen then escaped to space.

Water was removed from the atmosphere by chemical reactions with surface rock.
Ultraviolet light split the water molecules, and the hydrogen then escaped to space.
Earth has been gradually warming over the past few decades. Based on a great deal of evidence, scientists believe that this warming is caused by _____.


the fact that our politicians spout a lot of hot air

human activities that are increasing the concentration of greenhouse gases in Earth's atmosphere

the human release of chemicals called CFCs into the stratosphere

the increase in forest fires during recent years
human activities that are increasing the concentration of greenhouse gases in Earth's atmosphere
Which characteristic of Earth explains why we have an ultraviolet-absorbing stratosphere?

the existence of plate tectonics

the existence of oceans

the moderate surface temperature

the existence of photosynthetic life
the existence of photosynthetic life
Which jovian planet should have the most extreme seasonal changes?


Uranus
Saturn
Jupiter
Neptune
Uranus
Which planet may have helium rain in its interior, and what does this rain do?


Neptune, where it is restructuring the planet's interior.

Jupiter, where it may be an energy source for the Great Red Spot.

Saturn, where it generates heat as it falls downward.

Uranus, where it makes the ground wet.
Saturn, where it generates heat as it falls downward.
What would happen to Jupiter if we could somehow double its mass?


Its density would increase but its diameter would barely change.

Its density would stay about the same and its volume would double.

It would become a star, with nuclear fusion in its core.

Its density would decrease and its diameter would double.
Its density would increase but its diameter would barely change.
Which of the following gases is not a significant ingredient of the jovian planet atmospheres?

water
hydrogen
helium
carbon dioxide
carbon dioxide
Jupiter and the other jovian planets are sometimes called "gas giants." In what sense is this term misleading?


They are not in any sense "giants."

Actually, it's a great description, because these worlds are big and gaseous throughout.

The materials they are made of are not the kinds of thing we usually think of as gases.

They actually contain relatively little material in a gaseous state.
They actually contain relatively little material in a gaseous state.
Why is the radiation so intense in the region that traces Io's orbit around Jupiter (the Io torus)?


Io's gravity allows this region to capture huge numbers of charged particles from the solar wind.

The region is full of gases that become ionized after they are released from volcanoes on Io.

An orbital resonance between Io, Europa, and Ganymede makes the radiation intense.

Jupiter's strong magnetic field makes the radiation intense everywhere, and the region around Io is no different than any other region.
The region is full of gases that become ionized after they are released from volcanoes on Io.
Which statement about Saturn's rings is not true?


The rings must look much the same today as they did shortly after Saturn formed.

Some features of the rings are shaped by small moons that actually orbit within the ring system.

The large gap known as the Cassini Division is shaped by an orbital resonance with the moon Mimas, which orbits well outside the rings.

The rings are so thin that they essentially disappear from view when seen edge-on.
The rings must look much the same today as they did shortly after Saturn formed.
How can we determine the reflectivity of an asteroid?


By taking a photograph of it.

By measuring its mass and radius.

By comparing its brightness in visible light to its brightness in infrared light.

By where it is located in the asteroid belt.
By comparing its brightness in visible light to its brightness in infrared light.
In science fiction movies, spaceships are often shown dodging through large numbers of closely spaced, boulder-size objects. Which of the following real things in our solar system would look most like such science fiction dangers?


the rings of Saturn
the atmosphere of Jupiter
the asteroid belt
the Oort cloud
the rings of Saturn
When we see a meteor shower, it means that _________.


Earth is crossing the orbit of a comet

an Earth-approaching asteroid has recently come very close to our planet

the solar wind is unusually strong

you should duck and run for cover to avoid being blasted on the head by a rock from space
Earth is crossing the orbit of a comet
Why won't Pluto collide with Neptune?


Pluto is always much farther from the Sun than Neptune.

Actually, a collision of the two is inevitable within the next billion years.

Pluto orbits the Sun exactly 2 times for every 3 Neptune orbits, which ensures they never come close together.

Pluto's orbit never comes anywhere close to Neptune's orbit.
Pluto orbits the Sun exactly 2 times for every 3 Neptune orbits, which ensures they never come close together.
Suppose you find a meteorite made almost entirely of metal. According to current science, which of the following statements must be true?


Radiometric dating will show the age of your meteorite to date to the formation of our solar system.

Your meteorite was blasted off the surface of Mars by an impact.

Your meteorite is a fragment from the core of a large asteroid that shattered in a collision.

Your meteorite is a fragment of an object from the Kuiper belt.
Your meteorite is a fragment from the core of a large asteroid that shattered in a collision.
If we could put all the asteroids together, their total mass would be ______.


much less than the mass of any terrestrial planet

greater than the mass of Earth but less than the mass of Jupiter

about the mass of Mercury

about the mass of Earth
much less than the mass of any terrestrial planet
When you see the bright flash of a meteor, what are you actually seeing?


emission of visible light from a particle that has not yet entered Earth's atmosphere

a star that has suddenly shot across the sky

the glow from a pea-size particle and the surrounding air as the particle burns up in our atmosphere

the flash that occurs when a speeding rock from space hits the ground
the glow from a pea-size particle and the surrounding air as the particle burns up in our atmosphere
Suppose you are using the Doppler technique to look for planets around another star. What must you do?


Carefully examine a single spectrum of an orbiting planet.

Compare many spectra of the star taken over a period of many months or years.

Carefully examine a single spectrum of the star.

Compare many spectra of an orbiting planet taken over a period of many months or years.

Compare the brightness of the star over a period of many months or years.
Compare many spectra of the star taken over a period of many months or years.
All the following statements about known extrasolar planets are true. Which one came as a surprise to scientists who expected other solar systems to be like ours?


In some cases, we've found more than one planet orbiting the same star.

Some of the planets orbit their star more closely than Mercury orbits the Sun.

Most of the planets are quite massive - much more like Jupiter than like Earth.

Most of the planets orbit stars that are quite nearby compared to the scale of the entire Milky Way Galaxy.
Some of the planets orbit their star more closely than Mercury orbits the Sun.
In general, which type of planet would you expect to cause the largest Doppler shift in the spectrum of its star?


a massive planet that is close to its star

a massive planet that is far from its star

a low-mass planet that is close to its star

a low-mass planet that is far from its star
a massive planet that is close to its star
Why is it so difficult to take pictures of extrasolar planets?


No telescope is powerful enough to detect the faint light from a distant planet.

Their light is overwhelmed by the light from their star.

Extrasolar planets give off light at different wavelengths than planets in our solar system.

Telescopes are too busy with other projects.
Their light is overwhelmed by the light from their star.
The astrometric technique looks for planets with careful measurements of a star's _________.


velocity towards or away from us
brightness
position in the sky
all of the above
position in the sky
You observe a star very similar to our own Sun in size and mass. This star moves very slightly back and forth in the sky once every 4 months, and you attribute this motion to the effect of an orbiting planet. What can you conclude about the orbiting planet?


The planet must have a mass about the same as the mass of Jupiter.

You do not have enough information to say anything at all about the planet.

The planet must be closer to the star than Earth is to the Sun.

The planet must be farther from the star than Neptune is from the Sun.
The planet must be closer to the star than Earth is to the Sun.
Based on everything you have learned about the formation of our solar system, which of the following statements is probably not true?


Other solar systems will also have planets in the two basic categories of terrestrial and jovian.

Only a tiny percentage of stars are surrounded by spinning disks of gas during their formation.

Other planetary systems will have far more numerous asteroids and comets than actual planets.

Planets always tend to orbit their star in the same direction and approximately the same plane.
Only a tiny percentage of stars are surrounded by spinning disks of gas during their formation.
Why do sunspots appear dark in pictures of the Sun?


They are holes in the solar surface through which we can see through to deeper, darker layers of the Sun.

They actually are fairly bright, but appear dark against the even brighter background of the surrounding photosphere.

They are extremely hot and emit all their radiation as X rays rather than visible light.

They are too cold to emit any visible light.
They actually are fairly bright, but appear dark against the even brighter background of the surrounding photosphere.
Satellites in low-Earth orbits are more likely to crash to Earth when the sunspot cycle is near solar maximum because _________.


it is too dangerous to send the Space Shuttle to service satellites during solar maximum

Earth's upper atmosphere tends to expand during solar maximum, exerting drag on satellites in low orbits

of increased magnetic interference

they are more likely to have their electronics "fried" by a solar flare during solar maximum
Earth's upper atmosphere tends to expand during solar maximum, exerting drag on satellites in low orbits
Which of the following correctly compares the Sun's energy generation process to the energy generation process in human-built nuclear power plants?


The Sun generates energy through fission while nuclear power plants generate energy through fusion.

Both processes involve nuclear fusion, but the Sun fuses hydrogen while nuclear power plants fuse uranium.

The Sun generates energy through nuclear reactions while nuclear power plants generate energy through chemical reactions.

The Sun generates energy by fusing small nuclei into larger ones, while our power plants generate energy by the fission (splitting) of large nuclei.
The Sun generates energy by fusing small nuclei into larger ones, while our power plants generate energy by the fission (splitting) of large nuclei.
What do we mean when we say that the Sun is in gravitational equilibrium?


The hydrogen gas in the Sun is balanced so that it never rises upward or falls downward.

The Sun always has the same amount of mass, creating the same gravitational force.

The Sun maintains a steady temperature.

There is a balance within the Sun between the outward push of pressure and the inward pull of gravity.
There is a balance within the Sun between the outward push of pressure and the inward pull of gravity.
Which of the following best describes why the Sun emits most of its energy in the form of visible light?


Like all objects, the Sun emits thermal radiation with a spectrum that depends on its temperature, and the Sun's surface temperature is just right for emitting mostly visible light.

Nuclear fusion in the Sun's core produces visible light photons.

The visible light comes from energy level transitions as electrons in the Sun's hydrogen atoms jump between level 1 and level 2.

The Sun's gas is on fire like flames from wood or coal, and these flames emit visible light.
Like all objects, the Sun emits thermal radiation with a spectrum that depends on its temperature, and the Sun's surface temperature is just right for emitting mostly visible light.
The star Alpha Centauri A is the same type of star as the Sun, but its luminosity is about 1.6 times that of the Sun. What can we conclude?


Alpha Centauri A has a much higher surface temperature than the Sun.

Alpha Centauri A is much farther from Earth than the Sun.

Alpha Centauri A must have a vastly different interior structure than the Sun.

Alpha Centauri A fuses hydrogen into helium in its core at a higher rate than our Sun.
Alpha Centauri A fuses hydrogen into helium in its core at a higher rate than our Sun.
If the Sun's core suddenly shrank a little bit, what would happen in the Sun?


The density of the core would decrease, causing the core to cool off and expand.

The core would heat up, causing it to radiate so much energy that it would shrink even more.

The core would heat up, fusion rates would increase, the core would re-expand.

The core would cool off and continue to shrink as its density increased.
The core would heat up, fusion rates would increase, the core would re-expand.
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